1. Field of the Invention
The present invention relates to an outer-rotor type brushless fan motor, and more particularly, to an outer-rotor type brushless DC fan motor with forced-ventilation mechanism.
2. Description of the Related Art
Please refer to FIG. 1, a partially cross sectional view of a conventional outer-rotor type brushless DC fan motor 100 is illustrated.
As shown in FIG. 1, the conventional outer-rotor type brushless DC fan motor 100 comprises a rotor 101, a bearing assembly 201, a stator 301 and a plate 401. The rotor 101 is constituted by a shaft 102, a rotor case 104, a fan hub 103, and a permanent magnet 105 provided on an inner surface of a cup-shaped outer periphery of the rotor case 104. The bearing assembly 201 comprises at least one bearing 202 and a bearing housing 203, wherein the at least one bearing 202 is provided between the shaft 102 and an inner surface of the bearing housing 203. The stator 301 includes a plurality of silicon steel sheets 302 radially fixed to an outer surface of the bearing housing 203 and a set of coils 303 wound around each silicon steel sheet 302, wherein the cup-shaped outer periphery of the rotor case 104 encloses an outer edge of the stator 301, and the rotor 101 is rotated with respect to the stator 301. Furthermore, the plate 401 is fixed to the bearing housing 203 so as to support the outer-rotor type brushless DC fan motor 100.
However, when the conventional outer-rotor type brushless DC fan motor 100 runs, heat generated from the stator 301 enclosed in the DC fan motor 100 can not be dissipated effectively, resulting in the rated temperature of the running DC fan motor 100 being unable to reduce, and then the efficiency of the DC fan motor 100 being deteriorated at high temperature.
In view of the above, it is required an outer-rotor type brushless fan motor capable of reducing the temperature resulted from the running thereof and increasing the efficiency thereof.